Yeah, the 30 inches they say is so you see almost no lag in chnage in A/F from engine to the sensor, but like most shops do, they stick a wideband in the tailpipe. definetely not 30 inches from the port! With a V8 and without having to run 2 sensors to compare, the best place is just as close as possible to the engine in both exhaust paths, as long as its before the cats. the only thing that will change is the lag time between change in A/F of engine and registering on the wideband. but we're talking milliseconds here, so its not that huge of a deal.

 

If you are using a Bosch LSu sensor it actually works better behind the cats in blown or turbo apps. The sensor does not work above 750 deg C and any back pressure in the exhaust makes it drift off the scale, so this is why doing it behind the cat works well, Less heat and pressure makes it more stable. The cats have no time to really do anything at WOT so readings are just fine. If you have any tuning software just turn of one of the rear o2 sensors and use that bung. I have tried it both ways and the reading are the same exept its more stable and does not go drifting off making it look like its going lean from the heat and pressure. For alot of good information on this sensor check out this link and read the warnings. Link

 

When we tuned mine we took out the rear pass O2, turned it off with HP and put the wide band in there. Tuned it to 12.2 at WOT and 14.7 on the highway at cruise. When I had my last dyno session, the AFR layed right on 12.2. Putting the wideband BEHIND the cats allows the AFR to stabilize, better more consistent tuning.

Why install a bung when you have one already Just be sure to use some anti-seize!!

 

Good tip! Since I didn't get to get it in anyway, this past week. Just as I got things ready to be loosened, an 8" water main broke in front of my house. Flooded out my yard, and driveway, and had water in the basement. Needless to say, I didn't get the bung installed this week!

 

My dynojet wide band will be here today.
Now all I need is the new laptop and HPT.